Current stimulation to the brain partially restores
vision in patients with glaucoma and optic nerve damage: Randomized,
clinical trial shows that modulating brain plasticity offers a
promising avenue for vision restoration and rehabilitation --
ScienceDaily
Glaucoma slowly and silently clouds vision, without any pain.
Credit: Photo courtesy of NEI
Vision loss due to glaucoma or optic nerve damage is generally
considered irreversible. Now a new prospective, randomized,
multi-center clinical trial demonstrates significant vision improvement
in partially blind patients after 10 days of noninvasive, transorbital
alternating current stimulation (ACS). In addition to activation of
their residual vision, patients also experienced improvement in
vision-related quality of life such as acuity, reading, mobility or
orientation. The results are reported in PLOS ONE.
"ACS treatment is a safe and effective means to partially restore
vision after optic nerve damage probably by modulating brain
plasticity, re-synchronizing brain networks, which were desynchronized
by vision loss. This class 1 evidence is the first ever large-scale
multi-center clinical trial in the field of non-invasive brain
modulation using electric currents and suggests that visual fields can
be improved in a clinically meaningful way," commented lead
investigator Bernhard A. Sabel, PhD, of the Institute of Medical
Psychology, Medical Faculty, Otto-von-Guericke University of Magdeburg
(Germany).
In a study conducted at three German clinical centers (University of
Göttingen, Charité Berlin, and University of Magdeburg), 82 patients
were enrolled in a double-blind, randomized, sham-controlled clinical
trial, 33 with visual deficits caused by glaucoma and 32 with anterior
ischemic optic neuropathy caused by inflammation, optic nerve
compression (due to tumors or intracranial hemorrhage), congenital
anomalies, or Leber's hereditary optic neuropathy. Eight patients had
more than one cause of optic nerve atrophy.
The groups were randomized so that 45 patients underwent 10 daily
applications of ACS for up to 50 minutes per day over a two-week period
and 37 patients received sham stimulation. The only difference between
groups before treatment was that the stimulation group included more
men than the sham group; no other differences were found, including age
of the lesion or visual field characteristics. ACS was applied with
electrodes on the skin near the eyes. Vision was tested before and 48
hours after completion of treatment, and then again two months later to
check if any changes were long-lasting.
Patients receiving ACS showed significantly greater improvements in
perceiving objects in the whole visual field than individuals in the
sham-treated group. Specifically, when measuring the visual field, a
24% improvement was noted after treatment in the ACS group compared to
a 2.5% improvement in the sham group. This was due to significant
improvements in the defective visual field sector of 59% in the ACS
group and 34% in the sham group which received a minimal stimulation
protocol. Further analyses showed improvements in the ACS group at the
edges of the visual field. The benefits of stimulation were found to be
stable two months later, as the ACS group showed a 25% improvement in
the visual field compared to negligible changes (0.28%) in the sham
group.
Patient safety measures were maintained at a high level, in line with
previous studies. Current flow was assessed using sophisticated
computer simulation models. No participants reported discomfort during
stimulation, although temporary dizziness and mild headaches were
reported in rare cases.
The study results are in line with previous small sample studies in
which efficacy and safety were observed. Those studies revealed that
well-synchronized dynamic brain functional networks are critical for
vision restoration. Although vision loss leads to de-synchronization,
these neural networks can be re-synchronized by ACS via rhythmic firing
of the ganglion cells of the retina, activating or "amplifying"
residual vision. Dr. Sabel added that "while additional studies are
needed to further explore the mechanisms of action, our results warrant
the use of ACS treatment in a clinical setting to activate residual
vision by brain network re-synchronization. This can partially restore
vision in patients with stable vision loss caused by optic nerve
damage."
In summary, vision loss, long considered to be irreversible, can be
partially reversed. There is now more light at the end of the tunnel
for patients with low vision or blindness following glaucoma and optic
nerve damage.
